A table will be sized according to the content within it. The HTML tags for a table allow the table height to be specified as a percentage of the height of the containing HTML element. When the table is rendered, an extent rectangle can be drawn round it. An extent rectangle is the smallest rectangle that will completely enclose the table. This height property returns the vertical size of that extent rectangle.
Including height and width information on tables is optional, but it can significantly improve the performance of the layout engine as it renders the web page. This is because the layout engine does not need to wait until the table content has all been fetched before reserving sufficient space for it in the display.